Hello!
At the moment I´m constructing an active 3-way filter design for my new speaker project.
During calculating process I´ve got an idea:
Why not add a DC voltage to the audio signal after the input buffer, so the op-amps in the following stages always work with positive (or negative) amplitudes ?!?
In my opinion this would avoid zero-crossing dissortions!
(e.g. added DC +5V when audio signal range +/- 2,5 V -> chips work between +2,5 and +7,5 V)
The added voltage would be easy filtered by the coupling capacitor at the output .
Do you think this concept makes sense ???
greets
Peter
At the moment I´m constructing an active 3-way filter design for my new speaker project.
During calculating process I´ve got an idea:
Why not add a DC voltage to the audio signal after the input buffer, so the op-amps in the following stages always work with positive (or negative) amplitudes ?!?
In my opinion this would avoid zero-crossing dissortions!
(e.g. added DC +5V when audio signal range +/- 2,5 V -> chips work between +2,5 and +7,5 V)
The added voltage would be easy filtered by the coupling capacitor at the output .
Do you think this concept makes sense ???
greets
Peter
Fundamentally, the switch-over from one output device to the other happens at zero output current, not at zero voltage. There could be a significant voltage on the output at this instant; that doesn't matter (and this will always be the case with a reactive load, such as a filter). Once you realise that the N type output device can only ever source current, and the P type one can only ever sink current, you'll be closer to understanding.
CrazyChipMan said:Hello!
At the moment I´m constructing an active 3-way filter design for my new speaker project.
During calculating process I´ve got an idea:
Why not add a DC voltage to the audio signal after the input buffer, so the op-amps in the following stages always work with positive (or negative) amplitudes ?!?
In my opinion this would avoid zero-crossing dissortions!
(e.g. added DC +5V when audio signal range +/- 2,5 V -> chips work between +2,5 and +7,5 V)
The added voltage would be easy filtered by the coupling capacitor at the output .
Do you think this concept makes sense ???
greets
Peter
any time you couple DC into the input you are asking for noise -- even the best low noise regulators add 50 to 100uV, and off-the-shelf regulators add millivolts -- take a look at TI's website for a comprehensive discussion of single-supply opamp design because it discusses the problem in detail.
The cross over distorsions are not caused by the positive or negative
output voltage. They happen when the output CURRENT is changing the polarity. That's why analog_sa is proposing a current source.
The DC current load will keep the OP amp output stage in class A as long as the magnitude of the signal current is less than the DC-load.
The most simple and traditional method is to connect a resistor from the OP amp output to one of the rails. Depending on your chosen OP amp and circuit impedances and signal levels, this resistor should range between 10k and 1k5.
output voltage. They happen when the output CURRENT is changing the polarity. That's why analog_sa is proposing a current source.
The DC current load will keep the OP amp output stage in class A as long as the magnitude of the signal current is less than the DC-load.
The most simple and traditional method is to connect a resistor from the OP amp output to one of the rails. Depending on your chosen OP amp and circuit impedances and signal levels, this resistor should range between 10k and 1k5.
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